Sheaths for implantable fixation devices

ABSTRACT

A sheath for organizing soft tissue includes a first tube having a flexible body sized and shaped to receive a fixation device, and a second tube coupled to the first tube having a flexible body sized and shaped to receive a soft tissue graft. A method for implanting soft tissue in a bone tunnel includes coupling a soft tissue graft to a sheath assembly; and positioning the sheath assembly relative to the soft tissue graft based on a measured depth of a bone tunnel. A set of surgical devices for implanting soft tissue grafts in a bone tunnel includes a sheath assembly, a measurement device for measuring the depth of the bone tunnel, a securing element configured to secure the sheath assembly to the soft tissue graft at a position determined by the measured bone tunnel depth, and a tensioning device configured to organize a plurality of soft tissue grafts.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of copendingapplication U.S. Ser. No. 09/526,960, titled “SHEATHS FOR IMPLANTABLEFIXATION DEVICES,” filed Mar. 16, 2000.

BACKGROUND

[0002] The invention relates to devices that fix soft tissue to supportstructures, particularly devices that fix soft tissue grafts within bonetunnels.

[0003] In certain types of surgical procedures, soft tissue grafts mustbe fixed within a bone tunnel. For example, in anterior cruciateligament (ACL) replacement surgery, a ligament graft is harvested fromthe patient or from a donor, and implanted within the knee by securingone end within a bone tunnel drilled through the tibia, and the otherend within a bone tunnel drilled through the femur. Several ACLreconstructive techniques are described in Rosenberg, U.S. Pat. No.5,139,520, which is incorporated herein by reference.

[0004] Referring to FIG. 1, a ligament graft 10 can be fixed within abone tunnel using a bone screw 12. Graft 10 is made from e.g., a singleor double long strip of soft tissue. To implant graft 10, the middle ofthe strip (not shown) is first passed in a distal direction through afirst tunnel 14 in the tibia into a second tunnel 18 in the femur, andthen attached to the femur tunnel (or attached to bone adjacent thefemur tunnel) with a femur fixation device (not shown). Twoapproximately equal length segments 19 a, 19 b of the graft extendproximally from the attached middle portion through tunnels 18 and 14.The two ends 20 a, 20 b of segments 19 a, 19 b terminate proximal totibial tunnel 14. Segments 19 a and 19 b of the graft are then fixedwithin tibial tunnel 14 by inserting bone screw 12 between the twosegments, such that shaft 22 of the screw presses the segments againstinternal wall 24 of tunnel 14.

[0005] In attaching soft tissue within a bone tunnel using a bone screw,it is important that the tissue be rigidly fixed within the tunnel toprevent slippage. When the bone involved is relatively soft (lesscalcified), a common problem in elderly patients, screws may notadequately fix the graft to the bone.

SUMMARY

[0006] According to one aspect, the invention features a sheath fororganizing soft tissue including a first tube having a flexible bodysized and shaped to receive a fixation device; and at least one secondtube coupled to the first tube. The second tube has a flexible bodysized and shaped to receive a soft tissue graft.

[0007] Embodiments of this aspect of the invention may including one ormore of the following features.

[0008] A securing element secures the second tube to the soft tissuegraft. The sheath includes a third tube coupled to the first tube havinga flexible body sized and shaped to receive a soft tissue graft. Atleast one of the first tube and second tube is formed of a biocompatiblematerial selected from the group consisting of hydroxyapatite,polylactic acid, and polylactic glycolic acid. A guide is disposedwithin the second tube for facilitating threading of soft tissue throughthe second tube. A guide is disposed within the first tube forfacilitating advancement of a guide wire through the first tube. One endof the guide in the first tube has a funneled shape.

[0009] The first tube and the second tube are integrally formed. Theflexible bodies of the tubes have strands that form a mesh structure.The strands defines spaces therebetween. The flexible bodies of thetubes include a relieved wall that is perforated and defines a pluralityof holes therethrough. A major portion of the relieved wall is open. Theflexible body of the second tube has two ends and each end has anopening. The two openings are circular and have substantially the samedimensions. The first tube is smaller in diameter than the second tube.

[0010] According to another aspect, the invention features an assemblyincluding the sheath for organizing soft tissue and a fixation device.Embodiments of this aspect of the invention may include that thefixation device is a bone screw, and the flexible body of the first tubeis conformable to a shape of the shaft of the bone screw.

[0011] According to another aspect, the invention features a method forimplanting soft tissue in a bone tunnel. The method includes coupling asoft tissue graft to a sheath assembly; and positioning the sheathassembly relative to the soft tissue graft based on a measured depth ofa bone tunnel.

[0012] Embodiments of this aspect of the invention may include one ormore of the following features.

[0013] The method includes inserting the soft tissue graft and thesheath assembly into the bone tunnel, and inserting a fixation deviceinto the sheath assembly to fix the sheath assembly and soft tissuegraft inside the bone tunnel. The sheath assembly is fixed inside thebone tunnel such that an end of the sheath assembly is flush with anentrance to the bone tunnel. The method includes applying tension to thesoft tissue grafts during the insertion of the soft tissue grafts. Themethod includes organizing a plurality of soft tissue grafts so anapproximately equal tension can be applied to each graft.

[0014] Coupling a portion of a soft tissue graft includes inserting aportion of a soft tissue graft into the sheath assembly. The methodincludes providing the sheath assembly with a first tube including aflexible body sized and shaped to receive a fixation device and at leastone second tube coupled to the first tube and sized and shaped toreceive the soft tissue graft. The method includes inserting thefixation device, e.g., a bone screw, into the first tube to fix the softtissue graft inside the bone tunnel.

[0015] According to another aspect, the invention features a set ofsurgical devices for implanting soft tissue grafts in a bone tunnel. Theset includes a sheath assembly including a first tube and at least onesecond tube. The first tube is sized and shaped to receive a fixationdevice and the second tube is sized and shaped to receive a soft tissuegraft. The set includes a measurement device for measuring the depth ofthe bone tunnel; and a securing element configured to secure the sheathassembly to the soft tissue graft at a position determined by themeasured bone tunnel depth.

[0016] Embodiments of this aspect of the invention may include one ormore of the following features.

[0017] The set includes a device configured to organize a plurality ofsoft tissue grafts. The device includes a member having a first sectionand a second section. The member is configured such that a first softtissue graft is securable to the first section and a second soft tissuegraft is securable to the second section in response to manipulation ofonly the first section.

[0018] The securing element, e.g., a tie suture, is attached to thesheath assembly.

[0019] According to another aspect, the invention features a device forsecuring soft tissue grafts. The device includes a member having a firstsection and a second section. The member is configured such that a firstsoft tissue graft is securable to the first section and a second softtissue graft is securable to the second section in response tomanipulation of only the first section.

[0020] Embodiments of this aspect of the invention may include one ormore of the following features.

[0021] The member includes a first knob disposed on the first sectionand a second knob disposed on the second section. The first knob isknurled and manipulation of the first end is turning the first knob. Amating member is disposed on the first section and is configured to matewith the first knob. The second section includes a mating surfaceconfigured to mate with the second knob. A first spring is positionedbetween the mating member and first knob, and a second spring ispositioned between the mating surface and the second knob.

[0022] In an illustrated embodiment, a second member is coupled to thefirst member. The second member has a first section and a secondsection. The second member is configured such that a third soft tissuegraft is securable to the first section and a fourth soft tissue graftis securable to the second section in response to manipulation of onlythe first section.

[0023] The invention may include one or more of the followingadvantages.

[0024] The flexibility and thinness of certain implementations of thesheath allows the sheath to conform, e.g., to the shape of the fixationdevice, or to the shape of a bone tunnel.

[0025] The relief in the sheath, e.g., perforations in a wall of thesheath, allows in situ contact between a soft tissue graft and the wallof a bone tunnel, promoting development of Sharpy-like fibers andpermanent attachment of the soft tissue to the bone.

[0026] Therapeutic agents, such as osteoinductors or growth factors, canbe disposed on or embedded into the material of the sheath, allowingdelivery of the agent directly to the site of fixation.

[0027] Sheath implementations with multiple tubes allow multiple softtissue grafts to be fixed into a bone tunnel. The securing element maybe used to facilitate insertion of sheaths with multiple tubes bydecreasing the area of the cross-section of the inserted sheath andgrafts, and by fixing the sheath in place on the grafts. Guide tubes maybe used to facilitate insertion of grafts into the flexible tubes of thesheaths.

[0028] The tensioner device allows tension to be equalized amongmultiple grafts and organizes the grafts to permit easy introduction ofa fixation member. The tensioner device decreases the amount of workrequired to secure grafts by allowing two grafts to be secured to thetensioning device at opposite ends of the tensioning devicesubstantially simultaneously through the manipulation of only one knob.This allows the surgeon to hold two separate tendons and simultaneouslylock the tendons in place without requiring assistance from anotherperson.

[0029] Other implementations and advantages of the invention will beapparent from the following description and from the claims.

DESCRIPTION OF DRAWINGS

[0030]FIG. 1 is a sectional view of a prior art technique of fixing aligament graft within a tibial bone tunnel by using a bone screw;

[0031]FIG. 2A is a perspective view of a bone screw sheath;

[0032]FIG. 2B is a sectional view of the bone screw sheath of FIG. 2A;

[0033]FIG. 2C is a sectional view of the bone screw of FIG. 1;

[0034]FIG. 3 is a sectional view of a the bone screw and sheath of FIGS.2A-2C fixing a ligament graft within a bone tunnel in the tibia;

[0035]FIGS. 4 and 5 are sectional views illustrating alternativearrangements for the bone screw, sheath, and graft of FIG. 3 within thebone tunnel in the tibia;

[0036]FIG. 6 is a perspective view of an alternative embodiment of thesheath of FIG. 2A;

[0037]FIG. 7A is a perspective view of an alternative embodiment of thesheath of FIG. 2A that includes a washer;

[0038]FIG. 7B is a top view of the washer of FIG. 7A;

[0039]FIG. 8 is a perspective view of an alternative bone screw sheaththat includes two tubes;

[0040]FIG. 9 is a perspective view of an alternative bone screw sheaththat includes four tubes arranged to form a ring;

[0041]FIG. 10 is a perspective view of the bone screw sheath of FIG. 9with an external sleeve;

[0042]FIG. 11 is a flow chart of a surgical process to implant and fixsoft tissue grafts in a bone tunnel using a sheath;

[0043]FIG. 12 shows a surgical kit used to implant and fix soft tissuegrafts in a bone tunnel using a sheath.;

[0044]FIG. 13 is a perspective view of a sheath of the kit of FIG. 12;

[0045]FIG. 14 is a perspective view of a sheath assembly including thesheath of FIG. 13, guides, and a suture of the kit of FIG. 12;

[0046]FIG. 15A is a perspective view of an adjustable stop for a bonedepth measurement device of the kit of FIG. 12;

[0047]FIG. 15B is a cross-sectional view of the adjustable stop of FIG.15A;

[0048]FIG. 16 is a perspective view of a graft measurement and sheathpositioning assembly of the kit of FIG. 12;

[0049]FIG. 17 shows a scale extender element and EndoButton® holder ofthe kit of FIG. 12;

[0050]FIG. 18 is a perspective view of a tensioning device of the kit ofFIG. 12 including a tie rod assembly and a handle;

[0051]FIG. 19 is an exploded view of the tie rod assembly of FIG. 18;

[0052]FIG. 20 is a cross-sectional view of a rod assembly of the tie rodassembly of FIG. 19;

[0053]FIG. 20A is a cross-sectional view of a mating plate of the rodassembly;

[0054]FIG. 20B is a cross-sectional view of a knob of the rod assembly;

[0055]FIG. 21 is a perspective view of the handle of FIG. 18;

[0056]FIG. 22 is a cross-sectional view of the handle of FIG. 21;

[0057]FIG. 23 shows an end piece of an inner shaft assembly of thehandle of FIG. 21;

[0058]FIG. 24 is a perspective view of a tensioning device holder of thekit of FIG. 12;

[0059]FIG. 25 is a detailed flow chart of a surgical process to implantand fix soft tissue grafts in a bone tunnel using a sheath;

[0060]FIGS. 26A and 26B illustrate the threading of tendons through thesheath assembly of FIG. 14;

[0061] FIGS. 27A-27D illustrate the securing of two graft ends to thetensioning device of FIG. 18;

[0062]FIG. 28 illustrates the removal of the guides from the sheathassembly;

[0063]FIG. 29 illustrates the fixing of the sheath assembly to anadditional graft using the suture;

[0064]FIG. 30 illustrates the securing of two additional graft ends tothe tensioning device;

[0065]FIGS. 31A and 31B illustrate the tensioning of the grafts;

[0066] FIGS. 32-33B illustrate the positioning of the sheath assemblyand grafts within a knee joint; and

[0067]FIG. 34 is a cross-sectional view showing the sheath assembly andgrafts fixed in position within the bone tunnel in the tibia.

DETAILED DESCRIPTION

[0068] Embodiments of the invention feature sheaths that surround bonescrews and soft tissue grafts to improve fixation of the grafts. In itssimplest form, the sheath is a flexible, mesh tube that surrounds onlythe bone screw, both the bone screw and the graft, or only the graft. Inother embodiments, the sheath includes multiple tubes.

[0069] Referring to FIGS. 2A-2C, a sheath 50 has a tube-shaped body 52that defines a generally cylindrical exterior surface 53 and a generallycylindrical interior 54. Body 52 is formed from a biocompatible materialwoven into a mesh structure. The mesh defines numerous holes 56 thatexpose interior 54 to the outside. Sheath 50 also has two circular, openends 58 a, 58 b, allowing a tissue graft to pass entirely through theinterior of the sheath.

[0070] Interior 54 of sheath 50 is sized and shaped to receive bonescrew 12. Sheath 50 has an internal diameter D₁ greater than thediameter D_(S) of bone screw 12, so that both screw 12 and segments 19 aand 19 b of graft 10 can fit snugly within the sheath. The sheath has alength L₁ slightly larger than the length L_(S) of screw 12. The meshbody 52 is thin and flexible, allowing the sheath to adjust to snuglysurround the screw; body 52 can be compressed to reduce the volume ofinterior 54, twisted, or stretched. Since sheath 50 is thin and flexiblerather than rigid, it cannot on its own shore up soft bone, or fix agraft within a bone tunnel. (I.e., sheath 50 is not designed to be usedalone as a fixation device or as a solid, rigid reinforcement of softbone.)

[0071] In some embodiments, the threads forming the mesh body 52 arelarger in the radial direction than in the axial direction. Thisdifference in thread size results in sheath 50 being less flexibleradially than axially. In these embodiments, the diameter D₁ is moreresistant to expansion or contraction than length L₁. In otherembodiments, the thread size is equal throughout body 52.

[0072] Diameter D₁ is, e.g., between about 8 and 10 mm, and L₁ is,between about 25 and 40 mm. If sheath 50 is designed for a 7×25 bonescrew (7 mm diameter, 25 mm length), then L₁ is, e.g., about 30 mm, andD₁ is, e.g., about 9 mm. Most of exterior surface 53 is open. Forexample, about 40% of the area exterior surface 53 is mesh strands, andabout 60% is holes 56. The thickness T₁ of the mesh wall of sheath 50is, for example, less than about 0.3 mm, e.g., about 0.1-0.2 mm.

[0073] Body 52 can be made from a variety of bioabsorbable materials,including polylactic acid, or polylactic glycolic acid. Alternatively,body 52 can be made from a blend of absorbable materials, or from anon-absorbable material, such as a polyester. The material forming thebody preferably has a higher coefficient of friction than graft 10, sothat exterior surface 53 of the sheath grips internal wall 24 of bonetunnel 14 more firmly than graft 10 alone, improving fixation.

[0074] Body 52 can be formed, e.g., by weaving, braiding, knitting, orcrocheting strands of the material to form the cylindrical shape, or byextrusion, using techniques known in the art. The strands forming body52 have diameters of about 0.1-1.0 mm, e.g., 0.4-0.6 mm, or 0.51 mm.

[0075] Although sheath 50 can be used with a variety of fixation screws,screw 12 preferably has blunt or rounded screw threads, as opposed tosharp threads, so that the threads do not cut the sheath or the softtissue graft. A typical rounded-thread screw is shown in Roger et al.,U.S. Pat. No. 5,383,878, which is incorporated herein by reference.

[0076] Referring to FIG. 3, in operation, a surgeon first forms bonetunnels 14 and 18 within the tibia and femur, respectively. Next, graft10 is fixed to the femur tunnel using any technique known in the art(not shown). For example, the femur fixation device can include a loopattached to the femur at a distal end of femur tunnel 18. End 20 a ofthe graft is passed distally through tunnels 14 and 18, passed throughthe loop, and then pulled proximally through tunnels 18 and 14 until themiddle portion of the graft is centered on the loop. Alternatively, thegraft can be threaded through the loop prior to implantation of theloop. In addition, rather than using a loop, one end of graft 10 can befixed within the femur tunnel, allowing the other end to extendproximally through tunnels 18 and 14. To increase the number of segmentsavailable for fixation, multiple strips of soft tissue (i.e., multiplegrafts) can be separately attached to the femur. Various techniques forattaching a graft within a bone tunnel are described in Ferragamo, U.S.Pat. No. 5,769,894, which is incorporated herein by reference, and inRosenberg, supra.

[0077] After attaching graft 10 within (or adjacent to) femur tunnel 18,the surgeon passes ends 20 a, 20 b of graft 10 through interior 54 ofsheath 50 (via open ends 58 a and 58 b), and then slides sheath 50 intotibial tunnel 14. The diameter of tunnel 14 is only slightly larger thanthe outer diameter of sheath 50, such that sheath 50 fits snugly withintunnel 14. Alternatively, sheath 50 can be inserted into tunnel 14 priorto passing the graft through the sheath. To insert sheath 50 into tibialtunnel 14, the surgeon can use a delivery tool, such as a rigid tubedetachably fixed to the distal end of the sheath. Alternatively, asuture can be threaded through the distal end of sheath 50, and thesheath can be pulled into place within tunnel 14 using the suture.

[0078] The surgeon then inserts bone screw 12 into interior 54 of sheath50, between segments 19 a and 19 b of the graft. The screw may beinserted using an insertion tool known in the art, such as a screwdriver. When screw 12 is in place as shown in FIG. 3, the screw pressessegments 19 a and 19 b of the graft against the interior surface ofsheath 50, and presses exterior surface 53 of the sheath against wall24, fixing the graft within the tunnel.

[0079] As shown in FIG. 3, when screw 12 is inserted, it will typicallybe slightly off center, such that the screw's threads dig into wall 24of bone tunnel 14 along a segment 24 a of wall 24. For example, if screw12 has a major diameter of 9 mm, and a minor diameter of 7 mm, then thescrew threads will dig into wall 24 by about 1 mm along segment 24 a,where segment 24 a is about 120 degrees. This engagement of the threadswith segment 24 a of the wall helps hold screw 12 within tunnel 14, andtherefore improves fixation of graft 10 within the tunnel.

[0080] The presence of sheath 50 within bone tunnel 14 improves fixationof graft 10. Since exterior surface 53 of sheath 50 has a highercoefficient of friction than graft 10, sheath 50 is less likely thangraft 10 (which is made of tissue) to slide along wall 24 of the tunnel,or to twist when screw 12 is inserted into the tunnel. In addition,since body 52 of sheath 50 has a mesh structure, portions of graft 10protrude through holes 56 of the mesh, resisting sliding of graft 10relative to sheath 50. The flexibility of sheath 50 allows the sheath toconform to the shape of wall 24, maximizing the surface area contactbetween the exterior surface of the sheath and wall 24, therebyincreasing frictional forces between the sheath and the wall.

[0081] After screw 12 has been inserted into tunnel 14, the surgeon maytrim the portions of segments 19 a and 19 b that extrude proximally fromtunnel 14, completing the surgical procedure. Over time, graft 10permanently affixes to wall 24 by growth of Sharpy-like fibers betweenthe soft tissue of graft 10 and the bone tissue of wall 24.(“Sharpy-like fibers” are collagenous fibers that grow from bone into asoft tissue graft. The presence of Sharpy-like fibers indicate good bonygrowth to the graft, and therefore good fixation. See Pinczewski et al.,“Integration of Hamstring Tendon Graft With Bone in Reconstruction ofthe Anterior Cruciate Ligament,” Arthroscopy, 13: 641-43 (1997). Theopen holes 56 in body 52 of the sheath facilitate permanent fixation byincreasing the direct contact between the graft and the bone tunnelwall. Sheath 50 eventually dissolves, and new bone grows to fill itsposition.

[0082] To accelerate bone growth and permanent attachment of graft 10 towall 24, sheath 50 can include an osteoinductive agent, such ashydroxyapaptite, tricalcium phosphate, calcium sulphate, or a “ceramic”(a calcium and potassium crystalline). The osteoinductive agent can beapplied to sheath 50 prior to surgery by, e.g., spraying the sheath withthe agent, by dipping the sheath into a bath that includes the agent, bydusting or spraying the agent onto the sheath, or by filling the sheathwith a gel that includes the agent. In addition, the strands of materialforming the mesh body 52 can be hollow, and the agent can be within thehollow interiors of the strands. Alternatively, the agent can beincorporated into the material that forms body 52. For example, theagent can be blended into the material used to make the threads thatform mesh body 52, or can be added to the fibers as an osteoinductivefelt.

[0083] Other therapeutic agents, such as growth factors (e.g., tissuegrowth factor or platelet derived growth factor), bone morphogenicproteins, stem cells, osteoblasts, and cytokines, can also be includedin the sheath. These bioactive agents can be added using the techniquesdescribed above, or can be blended into the material that forms body 52using micro-encapsulation or nanoparticles. For example, body 52 can beformed from a material comprising microspheres of the agent and apolymer, such as polylactic glycolic acid. The microspheres of the agentand polymer can be prepared using known techniques. See, eg., Cohen etal., “Controlled Delivery Systems for Proteins Based onPoly(Lactic/Glycolic Acid) Microspheres,” Pharm. Research, 8:713-20(1991); DeLuca et al., U.S. Pat. Nos. 5,160,745 and 4,741,872. Ratherthan forming microspheres, the agent and polymer can also be mixedtogether using, e.g., sintering techniques. See, Cohen et al.,“Sintering Techniques for the Preparation of Polymer Matrices for theControlled Release of Macromolecules,” J. Pharm. Sciences, 73:1034-37(1984). The bioactive agents can also be attached to body 52 usingadhesives or electrical charge, or can be directly loaded onto thesheath by a delivery mechanism after implantation of the sheath.

[0084] Other embodiments are within the scope of the claims. Forexample, the sheath can be used to assist fixation of a bone screwwithin the femur tunnel 18, in addition to the tibial tunnel 14.

[0085] Referring to FIG. 4, screw 12 can be placed between sheath 50 andwall 24 of tunnel 14. In this embodiment, rather than inserting screw 12into the sheath after placement of the sheath within tunnel 14, screw 12is inserted into tunnel 14 along the side of the sheath. To hold screw12 to the side of the sheath, the sheath can optionally include anexternal loop 102. Loop 102 has a diameter slightly larger than thediameter of screw 12, so that shaft 22 of screw 12 fits snugly withinthe loop. Loop 102 can be made from the same material as body 52, or canbe made from an inflexible, rigid material.

[0086] When screw 12 is inserted, it compresses graft 10 within thesheath, and presses exterior surface 53 of the sheath against wall 24,fixing graft 10 within tunnel 14.

[0087] Referring to FIG. 5, segments 19 a and 19 b of graft 10 can bepositioned radially outside of sheath 50. In this embodiment, whensheath 50 is inserted into tunnel 14, it is located between ends 19 aand 19 b of the graft, so that the graft surrounds the sheath, ratherthan the sheath surrounding the graft. Screw 12 is then inserted intothe sheath, pressing segments 19 a and 19 b between exterior surface 53of the sheath and wall 24, fixing the graph in place. Alternatively, thescrew can first be inserted into the sheath, and then the sheath andscrew together can be positioned within the bone tunnel.

[0088] The structure of the bone screw sheath can be modified as well.The diameter D₁, length L₁, and thickness T of the sheath can be variedto accommodate different sized bone tunnels, different sized screws, anddifferent deployment methods. For example, in the deployment method ofFIG. 5, the inner diameter D₁ of the sheath can be approximately equalto the diameter D_(S) of the screw shaft, so that the screw fits verysnugly within the sheath, and exterior surface 53 of the sheath conformsto the shape of the screw shaft.

[0089] In the deployment methods shown in FIGS. 4 and 5, the sheath neednot be more rigid in the radial direction than in the axial direction.The threads forming the mesh body, therefore, are generally the samesize in both the radial and axial directions. In addition, sheaths usedin the deployment method of FIG. 5 can have less open space than sheathsused with the method of FIGS. 3 or 4. (I.e., less than 60% of thesheath's surface area will be holes.)

[0090] If the bone is particularly soft, sheath 50 can be woven tighter,so that the sheath is less flexible, thereby providing a more firmsubstrate for screw 12 to engage.

[0091] The sheath need not have a mesh structure. For example, thesheath can have a solid body with holes cut through the body, allowingcommunication between the exterior and interior of the sheath. Inaddition, the sheath's body need not be integrally formed. For example,the body can be formed by winding a strip of material around animplantable device to form a relieved body that defines an interior.

[0092] The sheath can have relief structures other than holes to allowcommunication between the exterior and interior. For example, othertypes of perforations, such as slits, can be used, instead of holes. Inaddition, the device can have a solid wall with thinned sections. Whenimplanted, the thinned sections biodegrade more quickly than othersections of the wall, such that in situ, the device developsperforations.

[0093] To increase the coefficient of friction of exterior surface 53 toimprove fixation of the sheath within the bone tunnel, exterior surface53 can have a roughened finish.

[0094] Referring to FIG. 6, rather than having two open circular ends,sheath 150 has an open end 158 a and a closed end 158 b. Closed end 158b gives sheath a “bag” or “sock” shaped structure.

[0095] Referring to FIG. 7A, a sheath 250 includes a washer 280 attachedto the proximal end 282 of the sheath. The washer 280 has a diameter D₂that is larger than diameter D₁ of sheath 250, and is larger than thediameter of the bone tunnel. Washer 280 prevents proximal end 282 of thesheath from passing into the bone tunnel when the screw is inserted intothe sheath, thereby ensuring that the sheath is ultimately positionedaround the screw shaft, rather than in front of the screw. Rather thanbeing circular, the washer can be square, triangular, or any othershape, so long as it has a dimension larger than the diameter of thebone tunnel. Referring to FIG. 7B, the upper surface 284 of the washercan include teeth or spikes 286 to grip bone, thereby reducing twistingof sheath 250 when a bone screw is inserted into the sheath. The washercan be made from a bioabsorbable material, or a non-absorbable,biocompatible material. In operation, the washer can be detached fromthe sheath after implantation of the graft and bone screw, or can beleft attached to the sheath.

[0096] Referring to FIG. 8, a sheath 350 includes two contiguous,parallel mesh tubes, 352 a and 352 b. Tubes 352 a and 352 b areintegrally woven, braided, knitted, or crocheted from threads. Each tubehas a diameter D₃ that is slightly larger than diameter D_(S) of screw12, and slightly less than diameter D₁ of sheath 50. Diameter D₃ can be,e.g., 2 mm, 4 mm, 6 mm, or 8 mm. Sheath 50 has a length L₃ approximatelyequal to the length of a fixation screw, e.g., about 10-50 mm, or 20-35mm. The walls 354 a, 354 b of tubes 352 a and 352 b each have athickness of, e.g., between 0.1 mm and 1.0 mm.

[0097] In operation, a soft tissue graft is passed through one of thetubes (e.g., tube 352 a), and the fixation screw is inserted into thesecond tube (e.g., tube 352 b). When the sheath, graft, and fixationscrew are positioned within the bone tunnel, tube 352 a is compressedbetween the screw and a wall of the bone tunnel. The graft, therefore,is compressed within tube 352 a, fixing the graft within the bonetunnel.

[0098] Referring to FIG. 9, a sheath 450 includes four parallel meshtubes, 452 a, 452 b, 452 c, and 452 d. The four tubes are arranged toform a ring 454. Ring 454 defines a central cavity 456 disposed betweenthe tubes. The cavity defines an axial bore that is coextensive with theaxial lengths of each of the tubes.

[0099] Each tube 452 a, 452 b, 452 c, and 452 d has a diameter D₄ and alength L₄ similar to diameter D₃ and length L₃ of sheath 350 (FIG. 8).As with sheath 350, the tubes of sheath 450 are integrally woven.

[0100] In operation, segments of a soft tissue graft are passed througheach of tubes 452 a-452 d. The surgeon can either use multiple,independent tissue grafts separately attached to the femur tunnel, orcan split the proximal end of a single graft into four separatesegments. The sheath is then inserted into the tibial bone tunnel, and afixation screw is inserted into central cavity 456. When the sheath,soft tissue, and screw are in place within the bone tunnel, the tubesare compressed between the screw and the bone tunnel wall, and the softtissue segments are compressed within each tube, thereby fixing the softtissue within the bone tunnel.

[0101] In the embodiment shown in FIG. 9, sheath 450 includes four tubesforming a ring. The sheath need not, however, be limited to this number.For example, the sheath can include a ring of 3, 5, 6, 7, or 8 tubes. Inaddition, soft tissue need not be passed through each tube. For example,soft tissue segments can be passed through two tubes, leaving theremaining tubes unoccupied.

[0102] Instead of being integrally woven, the tubes of sheath 450 can bewoven, braided, or knitted separately, and attached together using,e.g., stitching, spot welding, or an adhesive. The tubes can also besolid rather than mesh, and need not all have the same diameter. Inaddition, unlike the single tube sheaths of FIGS. 2A, 6, and 7, sheath450 can be rigid, rather than flexible.

[0103] Referring to FIG. 10, sheath 550 is identical to sheath 450 inall respects, except that sheath 550 further includes a mesh sleeve 580that surrounds the four tubes 552 a-552 d. Sleeve 580 is axiallycoextensive with tubes 552 a-552 d, and is integrally woven with thefour tubes. Alternatively, sleeve 580 can be a separate solid or meshstructure adhesively bound or otherwise coupled to the four tubes.Sleeve 580 acts to stabilize sheath 550, and facilitates insertion ofthe sheath into the bone tunnel. For example, to insert sheath 550, asuture or delivery tool can be attached to sleeve 580, rather thandirectly to one of the tubes.

[0104]FIG. 11 shows a flow chart of a surgical process 600 to implantand fix soft tissue grafts in a bone tunnel using a sheath. After softtissue grafts have been harvested in the usual fashion or otherwiseacquired, the soft tissue grafts are coupled to the sheath (602), e.g.,by inserting the grafts into the sheath and/or placing the graftsadjacent to the sheath. Concurrent, subsequent, or prior to coupling thegrafts to the sheath, the bone tunnel depth is measured (604).

[0105] The position of the sheath relative to the grafts is adjusted inaccordance with the measured depth of the bone tunnel (606). Adjustmentof the position of the sheath ensures that the sheath, once insertedinto the bone tunnel, is properly positioned in the bone tunnel toreceive the fixation device used to fix the grafts and sheath in thebone tunnel. For example, when the fixation device is a typicalinterference screw, the sheath is preferably placed such that one end ofthe sheath is flush with the entrance of the bone tunnel. Once properlypositioned, the sheath is fixed to the grafts to prevent movement of thesheath relative to the grafts during insertion into the bone tunnel(608) and after fixation of the sheath and graft assembly in the bonetunnel.

[0106] After insertion of the sheath and graft assembly into the bonetunnel, a fixation device, e.g., a bone screw, is inserted into the bonetunnel and is received by the sheath to fix the sheath and graftassembly in the bone tunnel (610) In another implementation, the graftis inserted first into the bone tunnel, and the sheath is subsequentlypushed up into the tunnel using an insertion tool.

[0107] More than one sheath can be coupled to a given graft andpositioned relative to the graft in accordance with the bone tunneldepth. For example, in ACL replacement surgery, a first sheath coupledto the grafts is positioned within the femoral side tunnel, and a secondsheath coupled to the grafts is positioned within the tibial sidetunnel.

[0108] Referring to FIG. 12, a surgical kit 700 used to implant and fixsoft tissue grafts in a bone tunnel includes a sheath 702 that is partof a sheath assembly 703, a measurement device 704 with an adjustablestop 706 for measuring the depth of a bone tunnel, a graft positioningboard 708 with an EndoButton™ holder 709 for facilitating coupling ofsheath 702 to the grafts and adjusting the position of sheath 702relative to the grafts, and a tensioning device 712 mounted to a holder714, which is coupled to board 708. The position of sheath 702 relativeto the grafts can be adjusted while the grafts are held in place bytensioning device 712. EndoButton® holder 709 includes a scale member711 and a scale extender element 710 for measuring the length of thegrafts to properly position the sheath in accordance with the measuredbone tunnel depth.

[0109] After insertion of the sheath and the grafts into the bonetunnel, a screw driver 716 is used to insert a screw 718 into the bonetunnel. Screw 718 is preferably tapered to facilitate insertion intosheath 702 and has blunt or rounded screw threads, as opposed to sharpthreads, so that the threads do not cut sheath 702 or the soft tissuegraft. Two screws 718 are included in kit 700, e.g., a 7×9×30 bonescrews (7 mm smaller diameter, 9 mm larger diameter, and 30 mm length)and an 8×10×30 bone screws (8 mm smaller diameter, 10 mm larger diameterand 30 mm length). The operator selects which bone screw to use basedupon graft size, tunnel size, and bone quality.

[0110] Referring to FIG. 13, sheath 702 includes three contiguous,parallel mesh tubes, 752 a, 752 b, and 752 c. Tubes 752 a, 752 b, and752 c can be, e.g., integrally woven, braided, knitted, or crochetedfrom threads. Alternatively, tubes 752 a, 752 b, and 752 c can beseparately woven, knitted, or crocheted but otherwise coupled together(e.g., by a suture or a sleeve). Tubes 752 a and 752 b have a diameterD₁ that is large enough to comfortably allow passage of a typical softtissue graft (e.g., 5 mm). Tubes 752 a and 752 b need not have the samediameter and may be sized in relation to the diameter of the soft tissuegraft designated to pass through each tube. Tube 752 c has a diameter D2large enough to allow passage of a guide wire used to guide a fixationdevice, e.g., a screw 718, into the bone tunnel (e.g., 2-3 mm).

[0111] Sheath 702 has a length L₁ in the range of, e.g., approximatelyone half the length of screw 718 to approximately the length of screw718 (e.g., 15-30 mm when the screw length is 30 mm). In someimplementations, tubes 752 a, 752 b, and 752 c can have differentlengths. The walls 754 a, 754 b, and 754 c of tubes 752 a, 752 b, and752 c, respectively, each have a thickness of, e.g., between 0.1 mm and1.0 mm.

[0112] Sheath 702 can be made from similar materials as described inreference to body 52. The material and configuration of tube 752 cprovides enough flexibility to allow tube 752 c to expand from a firstdiameter selected for passage of a guide wire (e.g., 2-3 mm) to a seconddiameter large enough to allow passage of screw 718 (e.g., 9-10 mm).

[0113] In another implementation, sheath 702 includes four outer tubesthat are circumferentially disposed around a central tube. The fourouter tubes are similar in structure to tubes 752 a or 752 b, and thecentral tube is similar in structure to tube 752 c. In use, four softtissue grafts are passed through the four outer tubes, and a fixationdevice is inserted into the central tube.

[0114] In yet another implementation, sheath 702 includes a first tubedisposed next to a second tube. The first tube is similar in structureto tubes 752 a or 752 b, and the second tube is similar in structure totube 752 c. In use, a single soft tissue graft is passed through thefirst tube, and a fixation device is inserted into the second tube.

[0115] In yet another implementation, the diameter of tube 752 c isequal to the diameter of tubes 752 a and/or 752 b. The diameter of tube752 c can be slightly larger than the smaller or larger diameter ofscrew 718 (e.g., 7 mm or 9 mm).

[0116] Referring to FIG. 14, sheath assembly 703 includes the sheath702, three guides 756 a, 756 b, and 756 c, and a securing element, e.g.,a suture 758. Guides 756 a, 756 b, and 756 c fit within tubes 752 a, 752b, and 752 c, respectively. The outer diameter D₁ of guides 756 a and756 b is slightly less than diameter D₁ of tubes 752 a and 752 b,respectively. Guides 756 a and 756 b define through channels 753 a and753 b, respectively, each having a diameter large enough to allowpassage of typical soft tissue grafts (e.g., approx. 5 mm). The lengthL₁ of guides 756 a and 756 b is, e.g., equal to, or preferably greaterthan the length L₁ of tubes 752 a and 752 b of sheath 702. Guides 756 aand 756 b are formed from, e.g., a biocompatible plastic material (e.g.,a poly ether-block co-polyamide polymer such as Pebax®) and thusfacilitate insertion of soft tissue grafts into tubes 752 a and 752 b bypreventing tubes 752 a and 752 b from collapsing or otherwise closingand obstructing graft insertion.

[0117] The outer diameter D2 of guide 756 c is slightly less thandiameter D2 of tube 752 c. Guide 756 c defines a through channel 753 chaving a diameter large enough to allow passage of a typical guide wire(e.g., approx. 2-3 mm). Guide 756 c preferably has a funneled end 757with a diameter D3 that facilitates insertion of the guide wire intotube 752 c. Guide 756 c has a length L2, which is longer than that ofthe sheath and guides 756 a and 756 b. Guide 756 c is formed from abiocompatible plastic material that is the same as or different thanthat of guides 756 a and 756 b.

[0118] Once the grafts are coupled to sheath 702, and sheath 702 isproperly positioned relative to the grafts in accordance with themeasured bone tunnel depth, as described further below, suture 758 isused to fix sheath 702 in position. The tie suture is, e.g., woven into,braided, or otherwise coupled to flexible mesh tubes 752 a, 752 b,and/or 752 c.

[0119] Referring to FIGS. 12, 15A and 15B, measurement device 704includes a handle 705, a rod 707 extending from handle 705, and anadjustable stop 706 having a cylindrical body 760 defining a cylindricalchannel 762 for slidably receiving rod 707. Body 760 defines a groove765 at an end 766 of channel 762 in which an o-ring 764 is positioned toensure a snug fit. Body 760 also defines a radial, threaded hole 770into which a thumb screw 767 with an engaging end 768 is inserted. Thumbscrew 766 is fixed in place by a set screw 772 inserted in a hole 774defined by a wall 776 of cylindrical body 760.

[0120] Referring to FIG. 16, a graft measurement and sheath positioningassembly 800 of kit 700 includes the graft positioning board 708 withattached EndoButton® holder 709 and scale extender element 710,tensioning device holder 714, and tensioning device 712 mounted toholder 714.

[0121] Referring also to FIG. 17, scale member 711 of EndoButton® holder709 includes an EndoButton® coupler 808 and a pin 806 for attachingEndoButton® holder 709 to board 708. Scale extender element 710 includesa hollow rectangular housing 850 sized and shaped to receive scalemember 711 of EndoButton® holder 709. Housing 850 includes arms 854 thatnormally protrude into the interior of the housing and are pushedoutwards by scale member 711. The frictional engagement of 711 againstarms 854 secures scale member 711 within scale extender element 710.Soft tissue grafts of a typical length (e.g., 120 mm), which otherwisewould extend beyond the length of scale member 711 of the EndoButton®holder 709 (e.g., 70 mm), are positioned on and mechanically supportedby the scale extender element 710.

[0122] Referring again to FIG. 16, tensioning device holder 714 iscoupled to board 708 by a coupler 812 that rides in a guide rail 814defined in board 708. Tensioning device holder 714 is movable in thedirection of arrow A along guide rail 814 to place grafts coupled toloop 804 under tension, and can be fixed in place using a screw 813 ofcoupler 812.

[0123] Referring to FIG. 18, the tensioning device 712 includes a tierod assembly 870 coupled to a handle assembly 872. Tie rod assembly 870includes a frame 874 that connects two parallel rod assemblies 876.Frame 874 defines a hole 878 bisected by an arch 880. Frame 874 includestwo parallel hollow tubes 875 that receive rod assemblies 876, which areattached to tubes 875 by pins 882.

[0124] Referring to FIGS. 19 and 20, each rod assembly 876 includes arod housing 884 that defines a cylindrical channel 886 sized and shapedto receive a rod 888, which is slidable within channel 886 relative torod housing 884. Rod housing 884 also defines bore holes 898 configuredto receive pins 882.

[0125] Rod 888 defines two slots 916 through which pins 882 pass. Theslots 916 limit axial movement of the rod 888 relative to rod housing884 along axis B to a maximum displacement distance L1 approximatelyequal to the width of the slots minus the diameter of pins 882. At oneend, rod 888 includes a threaded segment 918 and an end segment 920defining a groove 922 that accepts a retaining ring 924. At the otherend, rod 888 has a rod end 930 defining a groove 932 that accepts aretaining ring 934.

[0126] Rod housing 884 includes a first mating end 890 and a secondmating end 892. First mating end 890 is coupled to a knurled knobassembly 894, and second mating end 892 is coupled to a knob assembly896. First mating end 890 includes a mating surface 891 and alignmentposts 900. Second mating end 892 includes a mating surface 893 andalignment posts 908. Knurled knob assembly 894 includes a mating plate902 having a mating surface 901, which mates with surface 891 of end890, and a knurled knob 928 having a threaded post 926 into whichthreaded segment 918 of rod 888 is screwed. Knob assembly 896 includes aknob 910 having a mating surface 909, which mates with surface 893 ofend 892, and a non-threaded post 957 defining a bore 954 that receivesrod end 930.

[0127] Knurled knob 928 has a base 937 defining a cavity 936 partiallybounded by a threaded portion 940 that receives a threaded end plug 938.Threaded segment 918 of rod 888 extends through post 926 and into cavity936. Mating plate 902 is positioned between first mating end 890 andknurled knob 928. Referring to FIG. 20A, mating plate 902 defines a borehole 946 through which post 926 passes, and two recesses 948 that eachaccept an alignment post 900 and two recesses 948 a that each accept aspring 906. Alignment posts 900 limits any rotation between mating plate902 and mating end 890, and springs 906 are compression springs, whichact between mating surfaces 891 and 901.

[0128] Knob 910 has a base 956 defining a cavity 952 partially boundedby a threaded portion 960 that receives a plug 958. Referring to FIG.20B, knob 910 defines two recesses 948 b that each accept an alignmentpost 908 and two additional recesses 948 c that each accept a spring914. Alignment posts 908 limits any rotation between knob 910 and matingend 892, and springs 914 are compression springs, which act betweenmating surfaces 893 and 909.

[0129] With knurled knob 928 fully screwed onto threaded segment 918 ofrod 888, rod 888 is fixed in place with the respective mating surfacesengaged. When knurled knob 928 is loosened, rod 888 can move along axisB with slots 916 sliding along pins 882. Springs 906, 914 act to centerrod 888 between the knob assemblies 894, 896, and retaining rings 924,934 hold knobs 928, 910 onto the knob assemblies by contacting bases937, 956, respectively. In use, turning knob 928 loosens both knobs suchthat suture or other material to be retained can be positioned betweenthe mating surfaces of both knobs. Tightening knob 928 in turn tightensboth knobs to secure the suture in place. Both sutures are thus secured,one to each end of a rod assembly 876 of tie rod assembly 870, atsubstantially the same time through the turning of a single knob (i.e.,the knurled knob). Securing the sutures simultaneously and with only oneknob decreases the number of “hands” involved in this surgical step.

[0130] While the implementation of the tie rod assembly 870 shown inFIGS. 18-20 has two parallel rod assemblies 876, other implementationscan have only one rod assembly 876 or more than two rod assemblies 876,depending upon the number of strands of soft tissue to be implanted inthe bone tunnel.

[0131] Referring to FIG. 21, handle assembly 872 includes a handlesection 970, a sleeve 1006, and an inner shaft assembly 974 couplinghandle section 970 to sleeve 1006. Handle section 970 defines a slot 989and inner shaft assembly 974 has a pin 986 that slides within slot 989such that handle section 970 can be moved relative to inner shaftassembly 974. Sleeve 1006 defines a slot 1012 and inner shaft assembly974 has a pin 1004 that slides within slot 1012 such that sleeve 1006can be moved relative to inner shaft assembly 974. Handle section 970has a handle 970 a and a tubular extension 970 b.

[0132] Referring to FIG. 22, handle section 970 defines a through bore972 sized and shaped to receive inner shaft assembly 974. Sleeve 1006defines a through bore 1008 for receiving handle tubular extension 970 band inner shaft assembly 974. Inner shaft assembly 974 includes a shaft976 and an end piece 991 coupled to shaft 976 by a pin 998. Bore 972 hasan enlarged region 973 in which is positioned a spring 978 surroundingshaft 976. Spring 978 is positioned on shaft 976 between a shelf 990 ofshaft 976 and a bushing 980. Bushing 980 is positioned next to aretaining ring 982 which is attached to handle 970 and slidable relativeto inner shaft assembly 974. Positioned within sleeve 1008 and abuttinga distal end 970 c of handle section 970 and a shelf 976 a of shaft 976is a washer 984. Also positioned within sleeve 1008 between washer 984and a shelf 1010 of sleeve 1006 is a second spring 1014.

[0133] Referring to FIG. 23, end piece 991 includes a cylindrical member992 and a coupler 994. Cylindrical member 992 defines a bore hole 996for receiving pin 998 to couple cylindrical member 992 to shaft 976.Coupler 994 defines a slot 1000 for coupling handle assembly 872 to arch880, and a bore hole 1002 that receives a pin 1004.

[0134] The handle assembly 872 is attached to the tie rod assembly 870by pulling sleeve 1006 in the direction of arrow P relative to thehandle 970. Pulling sleeve 1006 compresses spring 1014 and exposescoupling slot 1000 of coupler 994. Arch 880 of tie rod assembly 870 isthen inserted into coupling slot 1000. Once arch 880 is inserted intoslot 1000, the pulling force is removed and spring 1014 automaticallyretracts the coupler 994 back into the sleeve 1006. Pin 1004 keepssleeve 1006 from sliding distally off handle 970 and inner shaftassembly 974.

[0135] Movement of handle 970 relative to inner shaft assembly 974against the force of spring 978 provides an indication of tensionapplied to handle 970 when handle assembly 872 is coupled to tie rodassembly 870. This relative movement causes pin 986 to slide along slot989. Slot 989 is marked accordingly to relate the movement of pin 986 toa tensile load (e.g., 1-100 Newtons). When a tensile load is imparted totie rod assembly 870 via coupler 994, spring 978 is compressed betweenretaining ring 982 attached to handle 970 and shelf 990 of inner shaft976. Compression of spring 978 results in movement of handle 970relative to inner shaft 976 and, thereby results in movement of tensionindicator pin 986 (attached to shaft 976) relative to slot 989 (definedby handle 970). A greater tensile load results in a greater compressionof spring 978, a correspondingly greater displacement of tensionindicator pin 986 relative to slot 989, and therefore, a greatermeasurement of tension.

[0136] Referring to FIGS. 16 and 24, tensioning device 712 is attachedto board 708 using device holder 714 and coupler 812. Tensioning deviceholder 714 includes a body 1020 with a vertical member 1022 from whichextends a small arm 1024 and a base arm 1026. Small arm 1024 has a lip1025 sized and shaped to fit within hole 878 of frame 874 (FIG. 18) suchthat one of the rod assemblies 876 can be positioned on a surface 1027of arm 1024. Base arm 1026 defines a groove 1029 in which the other rodassembly 876 is positioned. Device holder 714 includes a plug 1028attached to base arm 1026 by a pin 1030. Tensioning device holder 714 isattached to board 708 by inserting plug 1028 into coupler 812.

[0137]FIG. 25 shows a detailed flow diagram of a specific implementation1100 of surgical process 600 using kit 700 directed to ACL repair.Operations 1110, 1120, 1130, 1140, and 1150 correspond to operations610, 620, 630, 640, and 650, respectively.

[0138] Referring also to FIGS. 26A and 26B, initially, harvestedsemitendinosus and gracilis tendons 802 are sutured, folded, andinserted through a suture loop 1221 that couples the tendons to anEndoButton® 1220. The operator attaches EndoButton® 1220 to EndoButton®loop 804, and places the tendons on scale extender 710 of graftpositioning board 708 (1112). The operator then threads the gracilistendon ends 1200 a, 1200 b through guide tubes 756 a and 756 b of sheathassembly 703 (1114) using attached sutures 1202.

[0139] The operator measures the depth of the tibial and femur tunnelsusing measurement device 704 (1120). The depth of the bone tunnels ismeasured by inserting rod 707 of measurement device 704 into the bonetunnels until the distal end of the cylindrical probe rod reaches theend of the bone tunnels. The operator then advances adjustable stop 706up to the bone tunnel entrance by sliding stop 706 along rod 707, andsecures adjustable stop 706 in position using thumb screw 766. Rod 707is then removed from the bone tunnels, and the distance between stop 706and the distal end of the rod corresponds to the bone tunnel depth. Thisdepth measurement can be done at any time prior to operation 1138 (i.e.,prior to adjusting the position of the sheath 703 and fixing it inposition).

[0140] Referring to FIG. 27, the operator couples sutures 1202 attachedto tendon ends (e.g., gracilis tendon ends) 1200 a, 1200 b to tensioningdevice 712 mounted on tensioning device holder 714 (1132). Tensioningdevice holder 714 is fixed in any position along guide rail 814 thatprovides a distance between the tensioning device 712 and the sheath 702that conveniently allows subsequent insertion of tapered screw 718 intothe bone tunnel. First knurled knob 928 is loosened, and one suture 1202a is positioned between knurled knob 928 and mating plate 902, and asecond suture 202 b is positioned between knob 910 and mating surface893 (FIG. 19). Once both sutures are in position, the operator uses onehand to pull both sutures to the point where there is no slack in thesutures and the other hand to tighten knurled knob 928 to secure bothsutures to tensioning device 712.

[0141] Referring to FIG. 28, the operator then positions sheath 702relative to grafts 802 such that the distance between EndoButton® loop804 and the proximal end 702 a of sheath 702 corresponds to the measuredbone tunnel depth (1138). The guide tubes 756 a and 756 b are thenremoved from grafts 802, and tie suture 758 is used to fix sheath 702 inplace relative to grafts 802 (FIG. 29).

[0142] Referring to FIG. 30, the operator then couples sutures 1204attached to the two ends of the semitendinosus tendon 802 a to thetensioning device 712 as discussed above with reference to FIG. 27.

[0143] Referring to FIGS. 31A and 31B, the operator removes the softtissue graft assembly 1160, which includes EndoButton® 1220, thetendons, sheath 702, and tensioning device 712, from graft positioningboard 708 (1142), and attaches one or more sutures 1222 to EndoButton®1220 (FIG. 32). The operator then inserts sutures 1222 and EndoButton®1220 into the tibial tunnel and pulls on sutures 1222 using a block 1162to position the tendons within the bone tunnels (1144). Block 1162provides a mechanical advantage that facilitates pulling the EndoButton®loop, the tendons and the sheath 702 through the bone tunnels.

[0144] Referring to FIGS. 33A and 33B, once sheath 702 is pulled intoposition such that end 702 a of sheath 702 is flush with the entrance tothe tibial bone tunnel, the operator inserts a guide wire (not shown)into funneled end 757 of guide wire tube 756 c, removes guide wire tube756 c by sliding the guide wire tube out of tube 752 c of sheath 702 andover the guide wire, and then advances a tapered interference screw 718over the guide wire and into tube 752 c using screw driver 716 (1150).During advancement of the screw, the operator maintains the desiredtension on the tendons by pulling on handle assembly 970 whilemonitoring the position of the tension indicator pin 986 in slot 989.Use of the tensioning device during screw advancement provides theadvantage of equalizing the tension of the tendons and organizing thetendons to facilitate accurate positioning of the interference screw 718in tube 752 c of sheath 702. Driver 716 is conveniently inserted throughhole 878 of the tensioning device.

[0145] Referring to FIG. 34, when in position, EndoButton® 1220 is onthe surface 1228 of femur 1180, suture loop 1221 extends into the femurtunnel 1230, grafts 802 extend from suture loop 1221 in the femur tunnelto the tunnel 1232 in tibia 1182, and sheath 702 with interference screw718 are flush with the surface 1234 of the tibia. The gracilis tendongrafts and their surrounding tubes 752 a and 752 b as well as thesemitendinosus tendons are compressed between screw 718 (located in tube752 c) and the wall 1236 of the bone tunnel 1232 to fix the graftswithin the bone tunnel.

[0146] The sheaths need not be used exclusively with bone screws. Thesheaths can be used to improve fixation of other types of implantablefixation devices, such as soft tissue tacks, plugs, and suture anchors.The size and shapes of the sheaths can be varied to accommodate thedifferent types of fixation devices. The sheaths need not be used inbone tunnels. For example, soft tissue can be positioned inside asheath, and the sheath attached to the side of a bone with a fixationdevice such as a tack.

[0147] Knurled knob 928 need not be knurled. Knob 928 can instead have adifferent type of grippable surface that allows application of atorsional load without slipping (e.g., a scalloped or octagonalsurface).

[0148] Tensioning device 712, scale extender element 710, and adjustablestop 706 need not be used solely for soft tissue grafts but can insteadbe used for bone-tendon-bone grafts.

[0149] The displacement of sleeve 1008 relative to handle 970 can beused to indicate tension by adding scale markings to handle 970. Thesliding of handle 970 relative to sleeve 1008 provides an indicationsimilar to that provided by the sliding of pin 986 in slot 989. Therelative movement causes the scale markings on handle 970 to be exposedand to indicate the applied tension.

[0150] The process 1100 can be used for achilles tendons, fascia lata,or other harvested tendons. The EndoButton® or EndoButton® loop ofprocess 1100 may be replaced by an additional bone screw, a suturethrough a washer, a suture button, or a post.

What is claimed is:
 1. A sheath for organizing soft tissue, comprising:a first tube including a flexible body sized and shaped to receive afixation device; and at least one second tube coupled to the first tube,the second tube including a flexible body sized and shaped to receive asoft tissue graft.
 2. The sheath of claim 1, wherein the sheath includesa third tube coupled to the first tube, the third tube including aflexible body sized and shaped to receive a soft tissue graft.
 3. Thesheath of claim 1, wherein at least one of the first tube and secondtube comprise a biocompatible material selected from the groupconsisting of hydroxyapatite, polylactic acid, and polylactic glycolicacid.
 4. The sheath of claim 1, further comprising a guide disposedwithin the second tube for facilitating threading of soft tissue throughthe second tube.
 5. The sheath of claim 1, further comprising a guidedisposed within the first tube for facilitating advancement of a guidewire through the first tube.
 6. The sheath of claim 5, wherein one endof the guide has a funneled shape.
 7. The sheath of claim 1, wherein thefirst tube and the second tube are integrally formed.
 8. The sheath ofclaim 1, wherein the flexible body of the first tube comprises strandsthat form a mesh structure, the strands defining spaces therebetween. 9.The sheath of claim 1, wherein the flexible body of the second tubecomprises strands that form a mesh structure, the strands definingspaces therebetween.
 10. The sheath of claim 1, wherein the flexiblebody of the first tube includes a relieved wall.
 11. The sheath of claim10, wherein the relieved wall is perforated.
 12. The sheath of claim 10,wherein the relieved wall defines a plurality of holes therethrough. 13.The sheath of claim 10, wherein a major portion of the relieved wall isopen.
 14. The sheath of claim 1, wherein the flexible body of the secondtube includes a relieved wall.
 15. The sheath of claim 14, wherein therelieved wall is perforated.
 16. The sheath of claim 14, wherein therelieved wall defines a plurality of holes therethrough.
 17. The sheathof claim 14, wherein a major portion of the relieved wall is open. 18.The sheath of claim 1, wherein the flexible body of the second tube hastwo ends, each end having an opening.
 19. The sheath of claim 18,wherein the openings have substantially the same dimensions.
 20. Thesheath of claim 18, wherein the openings are circular.
 21. The sheath ofclaim 1, wherein the first tube is smaller in diameter than the secondtube.
 22. The sheath of claim 1, further comprising a securing elementfor securing the second tube to the soft tissue graft.
 23. An assembly,comprising: sheath for organizing soft tissue, including a first tubeincluding a flexible body sized and shaped to receive a fixation device;and at least one second tube coupled to the first tube, the second tubeincluding a flexible body sized and shaped to receive a soft tissuegraft; and the fixation device.
 24. The assembly of claim 23, whereinthe fixation device comprises a bone screw.
 25. The assembly of claim23, wherein the flexible body of the first tube is conformable to ashape of the shaft of the bone screw.
 26. A method for implanting softtissue in a bone tunnel, the method comprising: coupling a soft tissuegraft to a sheath assembly; and positioning the sheath assembly relativeto the soft tissue graft based on a measured depth of a bone tunnel. 27.The method of claim 26, further comprising inserting the soft tissuegraft and the sheath assembly into the bone tunnel.
 28. The method ofclaim 27, further comprising inserting a fixation device into the sheathassembly to fix the sheath assembly and soft tissue graft inside thebone tunnel.
 29. The method of claim 28, wherein the sheath assembly isfixed inside the bone tunnel such that an end of the sheath assembly isflush with an entrance to the bone tunnel.
 30. The method of claim 28,further comprising applying tension to the soft tissue grafts during theinsertion of the soft tissue grafts.
 31. The method of claim 26 furthercomprising organizing a plurality of soft tissue grafts so anapproximately equal tension can be applied to each graft.
 32. The methodof claim 26, wherein coupling a portion of a soft tissue graft comprisesinserting a portion of a soft tissue graft into the sheath assembly. 33.The method of claim 26, further comprising providing the sheath assemblywith a first tube including a flexible body sized and shaped to receivea fixation device and at least one second tube coupled to the first tubeand sized and shaped to receive the soft tissue graft.
 34. The method ofclaim 33, further comprising inserting the fixation device into thefirst tube to fix the soft tissue graft inside the bone tunnel.
 35. Themethod of claim 34 wherein the fixation device comprises a bone screw.36. A set of surgical devices for implanting soft tissue grafts in abone tunnel; the set including: a sheath assembly including a first tubeand at least one second tube, the first tube sized and shaped to receivea fixation device and the second tube sized and shaped to receive a softtissue graft; a measurement device for measuring the depth of the bonetunnel; and a securing element configured to secure the sheath assemblyto the soft tissue graft at a position determined by the measured bonetunnel depth.
 37. The set of claim 36, further comprising a deviceconfigured to organize a plurality of soft tissue grafts.
 38. The set ofclaim 37, wherein the device includes a member having a first sectionand a second section, the member configured such that a first softtissue graft is securable to the first section and a second soft tissuegraft is securable to the second section in response to manipulation ofonly the first section.
 39. The set of claim 36, wherein the securingelement is attached to the sheath assembly.
 40. The set of claim 39,wherein the securing element comprises a tie suture.
 41. A device forsecuring soft tissue grafts, the device comprising: a member having afirst section and a second section, the member configured such that afirst soft tissue graft is securable to the first section and a secondsoft tissue graft is securable to the second section in response tomanipulation of only the first section.
 42. The device of claim 41,wherein the member includes a first knob disposed on the first sectionand a second knob disposed on the second section.
 43. The device ofclaim 42 wherein the first knob is knurled and manipulation of the firstend comprises turning the first knob.
 44. The device of claim 43 furthercomprising a mating member disposed on the first section and configuredto mate with the first knob, and the second section includes a matingsurface configured to mate with the second knob.
 45. The device of claim44 including a first spring positioned between the mating member andfirst knob, and a second spring positioned between the mating surfaceand the second knob.
 46. The device of claim 41, further comprising asecond member coupled to the first member, the second member having afirst section and a second section, the second member configured suchthat a third soft tissue graft is securable to the first section and afourth soft tissue graft is securable to the second section in responseto manipulation of only the first section.